The second-largest time unit

The second-smallest time unit

The smallest time period

A record of Earth's history from its origin to the present

When many groups of organisms disappear from the rock record at around the same time

The three earliest eons that make up 90 percent of geologic time; during this time, Earth was formed and became hospitable to modern life

Scientists divide time into units based on ______ of ______ and ________.

TRUE or FALSE: The geologic time scale changes as scientists learn more about Earth.

The matching of unique rock outcrops or fossils exposed in one geographic region to similar outcrops exposed in other geographic regions.

States that an intrusion is younger than the rock it cuts across.

A rock or sediment layer that is used as a marker

States that the fragments, called inclusions, in a rock layer must be older than the rock layer that contains them

The principle that sedimentary rocks are deposited in horizontal or nearly horizontal layers

An educated guess of the order in which geologic events occur

The principle that in an undisturbed rock sequence, the oldest rocks are at the bottom and each consecutive layer is younger than the layer beneath it

Any erosional surface seperating two layers of rock that have been deposited at different times.

When a horizontal layer of sedimentary rock overlies another horizontal layer of sedimentary rock

When a layer of sedimentary rock overlies a layer of igneous or metamorphic rock, such as granite or marble

When horizontal sedimentary layer overlies tilted sedimentary layer

States that geologic processes occuring today have been occuring since Earth formed

A(n) ________ represents a gap of time in the rock record.

Geologists use ________ to compare rock layers in different geographic areas.

Enables scientists to determine the numerical age of rocks and other objects

The science of using tree rings to determine absolute age

The length of time it takes for one-half of the original isotope to decay

The emission of radioactive particles and the resluting change into other isotopes over time

Scientist use C-14 to determine the age of organic materials, which contain abundant carbon, in a process called _______ _______.

When scientists date an object using radioactive isotopes, they use a method called _________.

Bands of alternating light- and dark-colored sediments of sand, clay, and silt

_______ _________ and certain kinds of sediments help scientists determine the numeric age of many rocks.

The ______ rate of certain radioactive elements can be used as a kind of geologic clock.

True or False: Annual tree rings, ice cores, and sediment deposits can be used to date recent geologic events.

An object created when sediment fills a mold and becomes rock, shows what the outside of an organism looked like

a fossil that is found in the rock layers of only one geologic age and that is used to establish the age of the rock layers

a mark or cavity made in a sedimentary surface by a shell or other body

a fossilized mark that is formed in soft sediment by the movement of an animal

the changes in the characteristics of a species over several generations

When the original mineral is dissolved and almost simultaneously exchanged for another

When an organism's original skeletal material and even soft tissue is preserved. An example is when insects are preserved in amber.

fossils in which all the organic material has been removed and the hard parts of a plant or animal have been changed either by mineral replacement or by recrystallization

_______ provide evidence that species have evolved.

TRUE or FALSE: Fossils can only be preserved in one way.

____ ____ can help scientists correlate rock layers in the geologic record.

TRUE or FALSE: Fossils do not help scientists date rocks and locate reserves of oil, gas, and minerals.

What are fossils most often preserved in?

What is the name for an organism preserved by geologic processes?

Which of the following animals is commonly preserved in rock?

Which of the following kinds of animals are well preserved in amber?

Which of the following is an example of an organism whose tissue has been replaced by minerals?

How long have the La Brea asphalt deposits been trapping and preserving organisms.

How have fossils of mammoths that lived during the last ice age sometimes been preserved.

Which of the following statements about the fossil record is true?

The fossil record does NOT reveal which of the following?

What can scientist learn from studying the relationships between fossils?

Which of the following species would make a good index fossil?

How old would the rock surrounding a Tropites fossil be?

How old would the rock surrounding a Phacops fossil be?